Make the court-bouillon in fish poacher or roasting pan, and simmer, covered, for 30 minutes.
Wash and dry fish, sprinkle inside and out with salt and white pepper. If necessary, to make fish fit pan, cut off head and tail and place in the cavity of the fish. Wrap in cheesecloth and secure with string. Place in the court-bouillon, cover and simmer very slowly, six to eight minutes per pound. Turn once if court-bouillon doesn't cover the fish. When using several small fish, figure for the individual fish sizes, not the total weight. When done, the fish should flake easily and the flesh should lift cleanly from the bones. Lift the fish out of the liquid and place on a flat pan.
Remove the skin and row of bones along the top and bottom, and any dark meat of the fish. Position the head and tail on a serving platter. Lift the flesh from the top half of the fish and slide it onto a piece of foil, then invert on the platter between the head and tail. Remove the center bones from the fish in the cheesecloth, lift the bottom half and place on top of the other one on the platter. Remove all the skin and dark meat. Mold into a fish shape with your fingers. Cover and refrigerate. Discard all the skin, place the bones in the court-bouillon, and boil the liquid down to two cups. Strain and refrigerate. If using two six-pound fish, use one head and tail on the platter and stack the flesh to form a very fat fish (four fillets on top of each other) and proceed.
When the court-bouillon has jelled to a thick consistency, spoon it over the entire fish. Refrigerate again. Just before serving, cover thickly with the sauce (recipe below), decorate with parsley to cover the separation marks at the head and tail. Place radishes (or olives) in the eyes and a row of overlapping slices of lemon and hard-boiled eggs down the center. Garnish the platter with lettuce, cucumbers, tomatoes, olives, pimentos, and stuffed eggs. Serve extra sauce on the side.
Combine all the ingredients and mix to blend. Chill before using.